Device for applying electrode assemblies

ABSTRACT

The invention relates to a device comprising a number of electrode assemblies ( 10 ), which can be applied to the skin surface ( 4 ) of an animal or human being and by means of which voltages and currents can be tapped from the skin surface ( 4 ), and comprising a flexible, in particular extendable, retaining element ( 6 ) formed by a planar or film-like molded part. According to the invention, the electrode assemblies ( 10 ) comprise a main body ( 1 ) and a number of pin electrodes ( 2 ) that protrude from the main body ( 1 ) in the same direction, the electrode assemblies ( 10 ) are fastened to the retaining element ( 6 ), and the main body ( 1 ) of the respective electrode assembly ( 10 ) is connected to the retaining element ( 6 ), wherein the pin electrodes ( 2 ) of all electrode assemblies ( 10 ) protrude in the same direction.

The invention relates to a device for applying electrode assemblies tothe surface of the skin of an animal or human being, according to theindependent claim 1.

In the following the animal or human at whose skin voltages or voltagedifferences are to be determined will be referred to as the “patient”.

The inventive electrode assemblies are used in particular in the medicalfield for measuring brain currents or cardiac activity.

In the use of dry electrodes for detecting electrical signals in theinterior of the body of the patient, correct positioning of theelectrodes is an essential requirement. According to the state of theart, so-called spiders are used which fix the individual electrodes orelectrode assemblies to the body part of the patient on whichmeasurements are to be made, to provide maximal holding and problem-freecontact of the electrodes.

Spiders have a plurality of arms on the ends of which individualelectrodes are arranged. A problem with this is that the positions andorientation of the individual electrodes have to be adjusted to theparticular form of the patient, and therefore numerous differentadjustment steps have to be carried out in order to adapt the electrodesto the patient. A further problem is that the electrodes are only poorlyin contact with the patient and may easily slip out of place if thepatient moves.

The object of the invention is to make possible a simplified adaptationof the individual electrodes to the shape of the body, particularly ofthe head, of the patient, and thereby allow more rapid progress instudying multiple patients.

This object is achieved according to the invention by a device forapplying electrode assemblies to the surface of the skin of an animal orhuman, having the features of the predicate of the independent claim 1.

In a device with a plurality of electrode assemblies which may beapplied to the surface of the skin of an animal or human and with whichvoltages and currents from the skin surface may be tapped, which devicehas a retaining element which is a flexible, particularly extendableflat or film-like moulded piece, it is provided according to theinvention that the electrode assemblies each have a main body as well asa plurality of pin electrodes which protrude in the same direction fromthe main body, and the electrode assemblies are attached to theretaining element, further that the main body of a respective electrodeassembly is connected to the retaining element, the pin electrodes ofall of the electrode assemblies protruding in the same direction. Thisthereby allows simple positioning of the electrodes as well as simpleadaptation of the positions of the electrodes on the respective patient.

In order to improve the adaptation to special body parts, it may beprovided that the retaining element is in the form of a cover or asleeve.

It may further be provided that a pervasive recess is provided in themain body of at least one of the electrode assemblies and particularlyof all the electrode assemblies, through which recess a gel may beapplied to the skin surface, when the pin electrodes are applied againstthe skin surface, which gel reduces the contact resistance between theskin surface and the pin electrodes.

It is thereby possible to achieve improved contact of the pin electrodeswith the skin surface of the patient, thereby minimising the influenceof movements of the patient during the measurement. Moreover there isthe advantage that if the contact is sufficiently good it is possible toomit the use of a gel, thereby avoiding soiling of the patient with thegel. If it is possible to do without the use of a gel because ofsufficient contact, a time-consuming application of gel is not required.

In order to facilitate the application of gel to the respective skinlocations during measurement, it may be provided that the retainingelement has recesses, the respective position of which is adapted to theposition of each of the respective recesses in the main body, so that agel may be applied to the skin surface through the recesses in theretaining element and through the recess in the main body.

In order to achieve particularly good application to the body of thepatient, particularly in measurements of longer duration, it may beprovided that the main body is flat or plate-shaped with two oppositesurface regions, wherein the recess is a pervasive recess, and theboundary of the recess connects the two surface regions with each other.

For advantageous application of a gel to the pin electrodes and forreducing the contact resistance between the pin electrodes and the skinsurface, it may be provided that the pin electrodes are fixed to theboundary of the recess on the main body.

For optimum distribution of the applied gel, it may be provided that therecess is circular.

Further, in order to improve the application stability of the electrodeassembly to the skin of the patient, it may be provided that any twoadjacent pin electrodes are separated by the same distance.

In order to achieve improved contacting of the pin electrodes and toreduce transmission errors, it may be provided that the pin electrodesare arranged on a common electrode ring, wherein the electrode ring ispreferably comprised of the same material as the pin electrodes.

For advantageous penetration of the hair on the surface of the skin, andto achieve an advantageous application stability of the electrodeassembly on the skin of the patient, it may be provided that the number,arrangement, and height or length of the pin electrodes are such thatthe pin electrodes may penetrate through hair on the skin surface andmay provide a stable application; and/or that the height of the pinelectrodes is between 1 mm and 30 mm.

For advantageous distribution of the gel on the skin surface, it may beprovided that the area occupied by the surface of the main body of anelectrode assembly which is excised to form the recess is from 0.785 to700 mm², and/or the radius of the recess is between 1 mm and 30 mm.

In order to improve the contact between the skin surface and the pinelectrodes, and to improve the mechanical application stability, it maybe provided that the diameter of the pin electrodes is selected suchthat the pin electrode may penetrate through the hair on the skinsurface but does however not hurt the skin surface at a contact pressureallowing electrical contact; and/or that the diameter of the pinelectrodes is between 0.5 and 5 mm.

In order to improve the contact between the skin surface and the pinelectrodes, and to avoid injury to the patient, it may be provided thatthe ends of the pin electrodes which are distal from the main body arehemispherical.

For durable electrical contacting and reduction of the contactresistance and contact voltage, it may be provided that the pinelectrodes are highly conductive, and in particular are comprised ofgold, TiN, IrO₂, or of an alloy comprised of gold and/or TIN, IrO₂.

In order to avoid electrical disturbances, e.g. due to electromagneticinterference, it may be provided that an amplifier assembly is providedand the pin electrodes are connected to the amplifier assembly. In thisway, operation is possible even in the case of high skin resistance.

When the amplifier assembly is arranged on the main body, this enablessimplified contacting of the electrodes.

Optimal amplification with minimum noise is possible when the maximumdistance of the amplifier assembly to the closest pin electrode is lessthan 20 mm.

To facilitate easy exchangeability of electrodes as well as to reducethe number of amplifier assemblies, it may be provided that theamplifier assembly is arranged on a separate further main body which iselectrically and mechanically removable and connectable to the mainbody, in particular through catch connections.

In order to guarantee a simple structure of the device according to theinvention and rapid replacement of defective electrodes and replacementof amplifiers on further main bodies, it may be provided that theretaining element has a plurality of recesses, and the catch connectionsextend through the recesses of the retaining element.

The invention will be described with reference to a number of examples,with reference to the appended drawings, without limiting the generalinventive concept.

FIGS. 1 a and 1 b show two illustrations of an electrode assembly fromdifferent viewpoints. FIG. 1 c shows the electrode assembly incross-section. FIG. 2 a illustrates a side view of a separately formedamplifier circuit on a further main body which is contacted with theelectrode assembly illustrated in FIGS. 1 a to 1 c. FIG. 2 b shows across-section of the arrangement shown in FIG. 2 a. FIG. 3 a illustratesa cover with an electrode assembly and interior. FIG. 3 b illustratesthe cover shown in FIG. 3 a from the exterior. FIG. 4 illustrates aportion of a device for application against the skin surface, appliedagainst a patient, in cross-section.

FIG. 5 illustrates an alternative electrode assembly according to theinvention. FIG. 8 illustrates a separate amplifier circuit formed on acircuit board, which is contacted with an electrode assembly. FIG. 7illustrates a cover with a plurality of electrode assemblies. In FIG. 8,part of a device for application against the skin surface, applied to apatient, is shown in cross-section.

In FIGS. 1 a to 1 c, an embodiment of an electrode assembly 10 isillustrated. This comprises a main body 1 in the form of a circuitboard. The main body 1 is essentially flat and has a thickness of 1.2mm. The two surface areas 11 and 12 opposite to each other of the mainbody 1 are flat and parallel with each other. The main body 1 iscircular.

In the region of the boundary of the circular main body 1, eight pinelectrodes 2 are arranged which protrude from one of the surface regions11. The number of such electrodes 2 is advantageously more than 3, tofacilitate a mechanically stable application to the skin surface 4 ofthe patient 7 (FIGS. 4, 8). On the other hand, the number of electrodes2 is selected such that sufficient distance is provided between theelectrodes 2 to receive hairs, so that individual hairs of the patient 7do not become caught between the electrodes 2 and the skin surface 4.The distance between two adjacent electrodes 2 is approximately twicethe diameter of an electrode 2.

In the present embodiment, the pin electrodes 2 have a length of 7 mmand a diameter of 2.5 mm. The distal ends of the electrodes 2 have ahemispherical shape.

In the present embodiment, the pin electrodes 2 are comprised of puregold, with a minimum of impurities.

Alternatively, however, other alloys may however be used; wherein,advantageously, the pin electrodes 2 have low electrical resistance. Itis further advantageous if the pin electrodes 2 have high mechanicalstability, particularly flexural strength and breaking strength, e.g. asis typically the case with alloys of TIN or IrO₂.

The main body 1 has an electrically highly conductive electrode ring 14in its boundary region and in its area facing away from the pinelectrodes 2, which ring is comprised of a gold alloy and is soldered tothe pin electrodes 2. In the present embodiment, the electrode ring 14forms a part of the main body 1 and has the form of a hollow cylindricallayer with a layer thickness of 1.2 mm, an inner radius of 11 mm, and anouter radius of 17 mm. The part 14 a arranged in the interior of themain body 1 and surrounded by the electrode ring 14 is not conductive.

Alternatively, the entire main body 1 may be comprised of highlyconductive material, particularly electrode material.

Alternatively, the pin electrodes 2 may be welded or otherwiseelectrically conductively and mechanically connected to the electrodering 14.

On the surface region 12 opposite to the surface region 11 from whichthe pin electrodes protrude, a connecting piece 19 is provided which isconductively connected to the electrode ring and thus with theindividual pin electrodes 2. In the present case the connecting piece 19is in the form of a catch piece which may be removably connected to afurther connecting piece 19 a (FIGS. 2 a, 2 b). The connecting piece 19is also comprised of a material with good conductivity, in order toadvantageously pass on the signals determined by the pin electrodes 2.

In FIGS. 2 a and 2 b the electrode assembly 10 illustrated in FIGS. 1 ato 1 c is electrically and mechanically connected via the connectingpiece 19 to a further main body 15 which has a further connecting piece19 a which is electrically and mechanically connectable with theconnecting piece of the electrode assembly.

In this way, a two-piece electrode assembly is illustrated having theillustrated main body 1 as well as the structure of the pin electrodes 2corresponding to the embodiment illustrated in FIGS. 1 a to 1 c. Anamplifier assembly 13 is arranged on the further main body 15. The mainbody 1 and the further main body 15 are electrically conductivelyinterconnected by the respective connecting pieces 19 and 19 a, with thefurther main body having a connecting line 18 between the furtherconnecting piece 19 a and the amplifier 13. The catch connection betweenthe main body 1 and the further main body 15 is releasable andrestorable without suffering any mechanical damage. The output signal ofthe amplifier 13 is transmitted via a cable 13 a to a data processingunit.

In FIGS. 3 a and 3 b a retaining element 6 in the form of a cover 61 isshown, from the inside and from the outside, with only one electrodeassembly 10 and one further main body 15 being shown. The cover 61 isdesigned for application to the surface of the skin 4 on the head of apatient 7. The electrode assemblies 10 essentially correspond to theelectrode assemblies 10 illustrated in FIGS. 2 a and 2 b. The main bodyof the electrode assemblies 10 lies against the inner side of the cover61, with the further surface region 12 being in physical contact withthe inner surface of the cover 61. The pin electrodes 2 extend into theinterior of the cover 61. The cover 61 has recesses 62 in the regions ofthe catch connections 16 of the electrode assemblies 10, which recessesallow direct contacting with the further main body 15 (FIG. 4), so thatthe skin surface of the patient is directly electrically contactablethrough the cover 61.

The further main body 15 is on the outer side of the cover 61, whereinthe side toward which the further connecting piece 19 a is directed, isdirected toward the cover 61, and is in electrical and mechanicalcontact with the connecting piece 19 which passes through the recess 62in the cover.

In FIG. 4, the embodiment of the invention illustrated in FIGS. 3 a and3 b is shown in cross section. The cover 62 has, as shown in FIGS. 3 aand 3 b, a plurality of electrode assemblies 10 arranged on its innersurface. The recesses 62 in the sleeve 63 are penetrated by theconnecting piece 19 and 19 a of the main body of the electrode assembly10 and of the further main body.

An intermediate region filled with hairs between the skin surface 4 andthe main body 1 is shown hatched, designated subsequently by “hairregion 72”. The main body 1 and the skin surface 4 of the patient 7 areheld apart by the hair as well as by the pin electrodes 2.

FIG. 5 illustrates an alternative embodiment of an electrode assembly10. This is comprised of a main body 1 in the form of a circuit board.The main body 1 is essentially flat, with thickness of 1.2 mm. The twosurface regions 11 and 12 opposite to each other of the main body 1 areplanar and parallel. A circular recess 3 is formed in the main body 1.In this preferred embodiment of the invention, the diameter of therecess 3 is 5 mm, and thus the radius is 2.5 mm. The recess 3, i.e. theexcised surface of the main body 1 has an area of approximately 50 mm².

In the region of the boundary of the recess 3 there are seven pinelectrodes 2 which protrude from one of the surface regions 11.Advantageously, the number of pin electrodes 2 is more than three, tofacilitate a mechanically stable application to the skin surface 4 (FIG.8) of the patient 7 (FIG. 8). On the other hand, the number of pinelectrodes 2 is selected such that there is sufficient space between thepin electrodes 2 to receive hairs and to avoid a situation whereindividual hairs of the patient 7 become stuck between the pinelectrodes 2 and the skin surface 4. The distance between adjacent pinelectrodes 2 is approximately the diameter of a pin electrode 2.

In the present embodiment, the pin electrodes 2 have length 7 mm anddiameter 2.5 mm. The ends of the pin electrodes 2 which are distal fromthe main body 1 have a hemispherical shape.

In the present embodiment, the pin electrodes are comprised of pure goldwith a minimum of impurities.

Alternatively, however, other alloys may be used, wherein advantageouslythe pin electrodes 2 may have low electrical resistance. It is furtheradvantageous if the pin electrodes 2 have high mechanical stability,particularly flexural strength and breaking strength, e.g. as istypically the case with alloys of TiN.

The main body 1 has in the region of the recess 3 an electrically highlyconductive electrode ring 14 comprised of a gold alloy, to which the pinelectrodes 2 are soldered. The electrode ring 14 has a square crosssection of 10 mm×10 mm. The radius of the recess in the interior of theelectrode ring 14 is 5 mm, and the area of the recess is 50 mm².Alternatively, the pin electrodes may be connected to the electrode ring14 by welding or by other electrically conducting and mechanical means.The electrode ring 14 passes through the entire main body 1, wherein thesurface extending in the direction of the central recess of theelectrode ring 14 forms a boundary of a cylinder barrel form 31 of therecess 3 extending perpendicularly to the surface regions 11 and 12. Theelectrode ring 14 is connected to an amplifier assembly 13 (FIG. 8) by ahighly electrically conductive connecting line arranged on the furthersurface region 12 (not shown in FIG. 5). Advantageously, in thisembodiment this electrical connecting line is comprised of the sameelectrode material as the pin electrodes 2.

The amplifier assembly 13 is close to the individual pin electrodes, andin the present embodiment, for the purpose of minimising electromagneticdisturbances, the device 13 is arranged 4 mm away from the nearest pinelectrode 2.

FIG. 6 illustrates an alternative two-piece electrode assembly 10,wherein the main body 1 as well as the arrangement of the pin electrodes2 corresponds to the embodiment illustrated in FIG. 5. Unlike theembodiment illustrated in FIG. 5, the main body of the alternativeillustrated in FIG. 6 has a further main body 15 on which the amplifierassembly 13 is arranged. The main body 1 and the further main body 15are electrically conductively connected via respective connecting lines17 and 18 on the main body 1 and on the further main body 15, and via acatch connection 16. The catch connection 16 enables releasablemechanical connection of the main body 1 and the further main body 15.

In the present embodiment, the electrical connecting lines 17 and 18 arein the form of connecting layers on the surfaces of the main bodies 1and 15.

In FIG. 7 a retaining element 6 in the form of a cover 61, for beingapplied against the surface of the skin 4 on the head of a patient 7 isillustrated. The electrode assemblies 10 essentially correspond to thoseillustrated in FIG. 5. The main bodies 1 of the electrode assemblies 10lie on the interior of the cover 61, wherein the additional surface area12 is in mechanical contact with the inner surface area of the cover 61.The pin electrodes 2 extend into the interior of the cover 61. In theregions in which the recesses 3 of the electrode assemblies 10 arearranged, the cover 61 has recesses 62, so that a gel 5 (FIG. 8) may beapplied directly from the exterior through the cover 61 and onto theskin of the patient 7. In the embodiment illustrated in FIG. 7, forexample, this can readily occur because the recesses 62 of the cover 1are aligned with the recesses 3 of the main body 1 of the respectiveelectrode assembly 10.

Alternatively, however, it is also possible for the individual electrodeassemblies 10 to be inserted into individual recesses 62 of the cover61, with the cover 61 continuing in the region of its recess 62. In thiscase, the outer boundary of the electrode assembly 10 adjoins the innerboundary of one of the recesses 62 of the cover 61.

In FIG. 8 a part of a different embodiment of the invention is shown, inthe form of a sleeve 63 which is in operation with the patient 7. Thesleeve 63 has, similarly to the cover 61 shown in FIG. 7, a plurality ofelectrode assemblies 10 arranged on its inner surface. The recesses 62in the sleeve 63 are aligned with the recesses 3 in the main body 1 ofthe electrode assembly 10, so that a gel 5 may be applied to the skinsurface 4 of the patient 7. After the gel 5 is applied through therecess 3 it is arranged in the intermediate region filled with hair(indicated by hatched lines), hereinafter referred to as the hair region72, between the skin surface 4 and the main body 1. The main body 1 andthe skin surface 4 of the patient 7 are separated by the hair on the onehand and by the pin electrodes 2 on the other hand. The gel 5 diffusesinto the hair region 72 and reaches the application points 8 of the pinelectrodes 2 against the skin surface 4, used for substantially reducingthe contact resistance.

In a case when there is already sufficient electrical contact andsignals of sufficient quality for the respective study are available,the application of the gel 5 to the skin surface 4 in the hair region 72may be omitted.

Alternatively to the gel 5, an aqueous foam or a wet sponge (neitherillustrated) may be used, to be arranged in the recess 3 of the mainbody 1 and between the pin electrodes 2.

In order to prevent moisture or water from penetrating into theelectrode assembly 10, the electrically active components of theelectrode assembly 10 such as, e.g., the amplifier assembly 13, may havea waterproof design. The output signal of the amplifier 13 istransmitted by a cable (not shown in FIGS. 5 to 8) to a data processingunit.

Alternatively, it may be provided that the pin electrodes 2 are notcomprised entirely of gold and/or TiN and/or IrO₂ or an alloy of goldand/or TiN and/or IrO₂, but rather of a supporting body, e.g. comprisedof metal, which is only coated with one of the indicated highlyconductive alloys.

1. A device with a plurality of electrode assemblies (10) which may beapplied to the surface of the skin (4) of an animal or a human being,and by which electrode assemblies voltages and currents may be tappedfrom the skin surface (4), which device further has a flexible,particularly extendable, cover (6) which is formed with a flat orfilm-like moulded piece, wherein the electrode assemblies (10) each havea main body (1) and a plurality of pin electrodes (2) which protrude inthe same direction from the main body (1), and the electrode assemblies(10) are attached or connected to the retaining element (6), the mainbody (1) of a respective electrode assembly (10) is connected to theretaining element (6), and the pin electrodes (2) of all of theelectrode assemblies (10) protrude in the same direction; characterizedin that the pin electrodes (2) are arranged on a common electrode ring(14) and are electrically conductively connected with said ring, whereinthe electrode ring (14) is preferably comprised of the same material asthe pin electrodes (2).
 2. The device according to claim 1,characterized in that a pervasive recess (3) is provided in the mainbody (1) of one electrode assembly (10) and particularly of allelectrode assemblies (10), through which recess a gel (5) may be appliedto the skin surface (4), when the pin electrodes (2) are applied againstthe skin surface (4), which gel reduces the contact resistance betweenthe skin surface (4) and the pin electrodes (2).
 3. The device accordingto claim 2, characterized in that the retaining element (6) has recesses(62) the position of each of which is adapted to the position of one ofthe recesses (3) in the main body (1), so that a gel (5) may be appliedto the skin surface (4) through the recesses (62) in the retainingelement (6) and through the recess (3) in the respective main body (1).4. The device according to claim 2, characterized in that the mainbodies (1) of the electrode assemblies (10) are flat or plate-shapedwith two surface regions (11, 12), opposite to each other, wherein therecesses (3) in the main bodies (1) are pervasive recesses, and theboundaries (31) of the recesses (3) connect the two surface regions (11,12) of the main body (1) with each other, respectively.
 5. The deviceaccording to claim 1, characterized in that the pin electrodes (2) arefixed to the boundary of the recess (3) on the main body (1).
 6. Thedevice according to claim 1, characterized in that the recess (3) in theelectrode assembly (10) is circular.
 7. The device according to claim 1,characterized in that in each instance, any two adjacent pin electrodes(2) of an electrode assembly (10) are separated by the same distance. 8.The device according to claim 1, characterized in that the number,arrangement, and height or length of the pin electrodes (2) are suchthat the pin electrodes may penetrate through hair on the skin surface(4) and can provide a stable application, and/or in that the height ofthe pin electrodes (2) is between 1 and 30 mm.
 9. The device accordingto claim 1, characterized in that the area of the main body (1) which isexcised by the respective recess (3) of the electrode assembly (10) isfrom 0.785 to 700 mm², and/or the radius of the recess (3) is between 1and 30 mm.
 10. The device according to claim 1, characterized in thatthe diameter of the pin electrodes (2) is selected such that the pinelectrode (2) may penetrate through the hair on the skin surface (4) butdoes not hurt the skin surface at a contact pressure which allows anelectrical contact and/or that the diameter of the pin electrodes (2) isbetween 0.5 and 5 mm.
 11. The device according to claim 3, characterizedin that the ends of the pin electrodes (2) which are distal from themain body (1) are hemispherical.
 12. The device according to claim 1,characterized in that the pin electrodes (2) are highly conductive, andin particular are comprised of gold, TiN, or an alloy comprised of goldand/or TiN and/or IrO₂.
 13. The device according to claim 1,characterized in that, particularly on the main body of a respectiveelectrode assembly (10), an amplifier device (13) is provided orarranged, particularly at a distance of less than 20 mm from the closestpin electrode (2), and the pin electrodes (2) are connected to theamplifier device (13).
 14. The device according to claim 1,characterized in that the amplifier device (13) is arranged on aseparate, further main body (15) which is releasably electrically andmechanically connected to the respective main body (1), particularly viacatch connections (16, 19, 19 a).
 15. The device according to claim 16,characterized in that the retaining element (6) has a plurality ofrecesses (62), and the catch connections (19, 19 a) extend through therecesses (62) of the retaining element (6).